A risk assessment method for biological introductions

This article describes an application of a method for assessing risks assoc iated with the introduction of an organism into a new environment. The test organism was a binucleate Rhizoctonia fungal isolate that has potential fo r commercial development as a biological control agent for damping-off dise ases in bedding plants. A test sample of host plant species was selected us ing the centrifugal phylogenetic host range principles, but with an emphasi s on economic species. The effect of the fungus on the plant was measured f or each species and expressed on a logarithmic scale. The effects on weight s of shoots and roots per container were not normally distributed, nor were the effects on the number of plants standing (those which survived). State ments about the effect on the number standing and the shoot weight per cont ainer involved using the observed (empirical) distribution. This is illustr ated with an example. Problems were encountered in defining the population of species at risk, and in deciding how this population should be formally sampled. The limitations of the method are discussed.